With the development of mobile communications and increasingly scarce spectrum resources, it is often difficult for operators to obtain frequency spectrums with enough bandwidths within one frequency band. Each operator will more frequently establish a cross-band communication system in the future. This will cause communication device systems which are required to process cross-band ultra-wideband signals. Meanwhile, the operators' requirements for capital expenditure (CAPEX) and operating expense (OPEX) will gradually become a primary consideration when devices are selected. For a wireless communication base station system, about 80% of power consumption is generated by a radio frequency power amplifier (PA) in a radio remote unit (RRU) module. Thus, with the development of the digital mobile communication technology, high-efficiency power amplifiers (hereinafter referred to as power amplifiers) become a requirement which each of major system device manufacturers must meets. A major problem which the high-efficiency power amplifiers face is intermodulation interference generated when the power amplifiers operating close to a saturation region in a modern high-efficiency modulation mode, resulting in the power amplifiers generating serious nonlinear distortion. The digital pre-distortion technology becomes a basic power amplifier linearization function module of RRU systems in the current mainstream communication devices. In summary, the digital pre-distortion technology in the RRU systems is required to cope with cross-band ultra-wideband signals under the current operating condition.
This condition brings a challenge to systems using the power amplifier linearization technology. All the current digital pre-distortion technologies are based on an off-line self-adaptive and iterative technique in which digital pre-distortion information cannot always completely follows the change in actual links. This problem appears to be particularly prominent under the configuration of cross-band ultra-wideband signals. For instance, it may be discovered in the actual test that, in the mode mixing cross-band application of Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) signals and Time Division Duplexing-Time Division Long Term Evolution (TDD-LTE) signals, under certain configuration conditions, when a cell is initially established, data which is set by a predistorter to extract linearization parameters is single frequency band because of no service in service timeslots of a certain frequency band. When services in the frequency band are increased, the predistorter cannot update the linearization parameters in real time, after the cross-band signals in the actual test go through the linearization parameters extracted by the single frequency band, an abrupt change of more than ten dBs will occur in output power, and the frequency spectrum is abnormal, which easily causes damage to the power amplifiers of the systems and huge harm to system robustness.